fix(members): make sure the member's inner user is updated (#2970)

* fix: make sure the member's inner user is updated when fetched

* chore: add changelog

* style(pre-commit): auto fixes from pre-commit.com hooks

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: Soheab

CHANGELOG.md

@@ -89,6 +89,9 @@ These changes are available on the `master` branch, but have not yet been releas
   parameters. ([#2952](https://github.com/Pycord-Development/pycord/pull/2952))
 - Fixed autocomplete crashing when using an async staticmethod.
   ([#2966](https://github.com/Pycord-Development/pycord/pull/2966))
+- Fixed attributes like :attr:`Member.display_banner` being `None` when the member has
+  no guild specific banner, but does have a global one.
+  ([#2968](https://github.com/Pycord-Development/pycord/pull/2949))
 
 ### Deprecated
 

discord/state.py

@@ -357,13 +357,21 @@ def _update_references(self, ws: DiscordWebSocket) -> None:
     def store_user(self, data: UserPayload) -> User:
         user_id = int(data["id"])
         try:
-            return self._users[user_id]
+            user = self._users[user_id]
         except KeyError:
             user = User(state=self, data=data)
             if user.discriminator != "0000":
                 self._users[user_id] = user
                 user._stored = True
             return user
+        else:
+            # Making sure we don't mutate the cached user
+            # because we cannot make sure it's up to date.
+            # but still return the updated version of the user.
+            # This make sure data like banner, etc are updated.
+            copied_user = user._copy(user)
+            copied_user._update(data)
+            return copied_user
 
     def deref_user(self, user_id: int) -> None:
         self._users.pop(user_id, None)